In conventional CMOS sensors, the circuitry for a plurality of photo-diodes is shared. The pixels may include two photo-diodes located in neighboring rows that share the same circuitry. Such a shared circuit concept can result in having two metal bus lines in the row direction and two metal bus lines in the column direction per photo-diode as shown in FIG. 1.
Circuit 100 represents the schematic diagram of a four transistor (4T) shared circuit pixel with two photo-diodes 107 and 108. The photo-diodes are coupled through charge transfer transistors 109 and 110 respectively to a common floating diffusion (FD) charge detection node 115. The FD node 115 is connected to the gate of the source follower (SF) transistor 112, whose drain is connected via line 116 to the Vdd column bus line 101. The source of the SF is connected via the address transistor Sx 113 and line 117 to output signal column bus line 102. The FD node is reset by transistor 111 whose drain is connected to line 116. The control signals to the address transistor 113, the reset transistor 111, and charge transfer transistors 109 and 110 are supplied by the row bus lines 114, 106, 104 and 105 respectively. As can be seen from the schematic diagram, the circuit that has two photo-diodes, and includes two row bus lines and two column bus lines per photodiode. In conventional circuits, it is also necessary to provide an additional connections between the elements of the circuit in the column direction as is illustrated by the wire 103.